Question

我有一个列ID varchar（255）和done位的表。我想要获取找到的第一个ID，其中未设置该位，同时取出也设置该位。因此，该脚本的其他任何实例都不会使用相同的ID，也不会出现竞争条件。

import _mssql
con = _mssql.connect(server='server', user='user', password='password', database='default')

#these two in a single command
con.execute_query('SELECT TOP 1 ID FROM tableA WHERE done=0')
con.execute_query('UPDATE tableA SET done=1 WHERE ID=\''+id_from_above+'\'')
for row in con:
    #row['ID'] contains nothing as it last used with the UPDATE, not the SELECT
    start_function(row['ID'])

编辑（包括wewesthemenace的建议）：

[...]
con.execute_query('UPDATE tableA SET done = 1 WHERE ID = (SELECT TOP 1 ID FROM tableA WHERE done = 0)')
for row in con:
    #row['ID'] contains nothing as it last used with the UPDATE, not the SELECT
    start_function(row['ID'])

使用Microsoft SQL Server Enterprise Edition v9.00.3042.00，即SQL Server 2005 Service Pack 2

编辑2：
回答的问题引出了一个后续问题：While mssql query returns an affected ID use it in a while loop

Answer 1

这个怎么样？

UPDATE tableA SET done = 1 WHERE ID = (SELECT TOP 1 ID FROM tableA WHERE done = 0)

Answer 2

可能的解决方案，适用于我的情况。

con.execute_query('UPDATE tableA SET done=1 OUTPUT INSERTED.ID WHERE ID=(SELECT TOP(1) ID FROM tableA WHERE done=0)')
for row in con:
    #row['ID'] is exactly one ID where the done bit wasn't set, but now is.
    start_function(row['ID'])

在MSSQL中更新并选择一个操作

2 个答案: